Large vehicles, such as the automobile, have a typically fuel injected engine and a fuel pump subassembly mounted inside a fuel tank. The fuel tank is generally hidden from view and mounted to the undercarriage of the vehicle. Various penetrations and protrusions, such as a tank access hole for insertion of the fuel pump subassembly into the tank, are typically located at the top of the tank to minimize any opportunity of fuel leakage. A top mounted flange supports the fuel pump subassembly and covers and seals the access hole. Location of the flange and various protrusions projecting outward from the flange at the top of the tank protects the flange from abusive road conditions. Because the tanks are concealed by the undercarriage of the vehicle, any negative cosmetic impact of the top mounted flange is of no consequence. Moreover, any noise produced by the fuel pump is likely not to disturb the vehicle occupants because of the remote location of the fuel tank and because of the vibration dampening and noise absorbing characteristics of the plastic used to manufacture the tank.
For smaller recreational vehicles such as motorcycles, industry trends are turning away from the typical gravity feed carburetors and are leaning toward the use of fuel injection systems similar to larger vehicles. Location of the fuel pump inside the relatively small tank of a motorcycle would be preferred because it could reduce the number of fuel hose and electrical connections and also decrease fuel vapor emissions and the chance of fuel leakage into the surrounding environment while providing a modular design which simplifies assembly and reduces manufacturing costs. Unfortunately, the introduction of a fuel pump subassembly inside the tank of such a small recreational vehicle is difficult because: the fuel tank is visually exposed and typically mounted near the top of the recreational vehicle making cosmetic appearance and thus the location of the pump subassembly flange a concern; the tank is relatively small making pump placement difficult; and the tank is typically made of metal which contributes to the proliferation of pump noise.
Because the fuel tank is visually exposed in a motorcycle application, the tank is traditionally decorated thus contributing to a cosmetic theme of the motorcycle. Often, the shape or general appearance of the tank is identifiable to a particular manufacturer, thus having trademark value, thus making cosmetic alterations for the addition of a fuel pump subassembly undesirable. Moreover, the operator of the recreational vehicle or motorcycle is often located directly adjacent to the fuel tank, hence, the tank is preferably smooth, having minimal protrusions which could potentially cause injury to the operator or rider. For example, the fuel tank of a motorcycle is disposed generally between the legs of the rider. Consequently, the tank is preferably “tear-drop” in shape having the larger globe portion positioned toward the front of the motorcycle while tapering off and sloping downward toward the motorcycle seat creating a substantially smooth transition between the tank and the seat. For motorcycle applications, the only protrusion which could typically come between the ergonomically friendly fuel tank and the rider is the fuel filler cap. However, the cap is relatively low and smooth in profile and is located toward the forward top of the tank at the larger globe portion of the “teardrop.” The visually exposed placement of a flange, with associated fuel hoses and a wire harness, at the top of the fuel tank would not only crowd the filler cap, but would destroy the pleasing cosmetic appearance of the tank, expose the flange to possible damage and expose the rider to possible injury.
Moreover, the close proximity of the fuel tank to the rider makes the rider sensitive to noise emanating from the fuel tank. Because the motorcycle tank is traditionally made of steel, for strength and the adherence of paint, vibration induced noise caused by a running pump inside the tank is likely to be annoying to the rider. Furthermore, the running vibration characteristics of the motorcycle can be transmitted to the pump causing damage to pump components.